1. Field of the Invention
The present invention relates to the field of medium power bidirectional switches, and for example of bidirectional switches connectable on the electric A.C. supply network, capable of withstanding voltages of several hundreds of volts.
2. Discussion of the Related Art
Among known medium-power bidirectional switches, triacs have the advantage of being able to withstand voltages of one polarity or the other, that is, they can be directly placed in a circuit supplied by an A.C. supply network, and further have the advantage of being able to be controlled by a positive or negative gate signal.
However, a disadvantage of triacs is that they are controlled by injection of a current. In many cases, it would be preferred for this control to be performed by a voltage, that is, for the triac to turn on when the voltage applied to its control terminal becomes greater, in absolute value, than a determined threshold.
A known solution to overcome this disadvantage is to arrange, in series with the gate terminal of a triac, a diac or bidirectional Schottky diode, which turns on when the voltage thereacross exceeds a determined threshold. However, despite the many attempts performed, the monolithic integration of a triac or of a diac has never been achieved in a commercially exploitable manner.